THF-herwinning uit 'n brisantstofafvalstroom

Bredenkamp, Julane (1990-03)

Thesis (MScIngwet)--University of Stellenbosch, 1990.

Thesis

ENGLISH SUMMARY: Hexanitrostilbene (HNS) is a high explosive which is manufactured locally on a pilot plant scale and used on an experimental basis as an additive in RDX/TNT fillings for the ISS mm explosive shell. A programme to establish technology for the manufacture of HNS was launched to collect data for the design of production scale equipment. Tetrahydrofuran (THF) is used as a solvent in the synthesis of HNS and is by far the most expensive component involved in the synthesis of this explosive. As part of the HNStechnology programme an investigation was launched into the recovery of THF from the effiuent stream. The investigation involved three facets, namely: - A qualitative investigation, on a laboratory scale, to evaluate the feasibility of distillation as a method of recovery. - A small scale investigation during which the recovery of THF was investigated by continuous as well as batch distillation procedures. - An investigation, on an intermediate scale, to develop a definite procedure for use by production personnel for THF recovery. The laboratory scale investigation A laboratory scale recovery facility was constructed using standard glass equipment and instrumentation. In the first phase of the programme, solvent mixtures which simulated the HNS effiuent stream were used as distillation feedstock because the risk associated with the distillation Of actual effiuent (which contains small amounts of high explosives) was not known. It was shown that THF could be recovered at favourable yields and acceptable purities from the simulated effiuent stream. Treatment of the effiuent stream with HCI and extraction solvents to remove unwanted components before distillation was investigated next. The precipitation of dissolved high explosive products with HCI was successful, but the extraction of THF With pentane, toluene and xylene adversely affected the yield and purity of the recovered product and was therefore not further pursued. In a subsequent investigation the actual effiuent stream was used as distillation feedstock. It was shown that the effiuent stream can be subjected to atmospheric distillation without danger of explosion. The small scale investigation As mentioned previously, HNS is a development product which is being manufactured and used on a purely experimental basis; its probable concentration as an additive in RDX/TNT fillings has not been quantitively evaluated. Because of this, it was not known in what quantities HNS would be used and manufactured in future; consequently projections as to the volume of effiuent arisings from which THF would have to be recovered have also not been possible. In the light of this it was decided that the recovery of THF from the HNS effiuent stream should be investigated by continuous as well as batch distillation. For the investigation into the recovery of THF on a small scale, modular distillation apparatus was designed and manufactured from glass. A large number of experimental runs was done during which several equipment problems were identified and solved by means of modifications. Results showed that continuous separation was impracticable and the apparatus was therefore modified for batch distillation. The intermediate scale investigation Stainless steel apparatus was designed and erected for the investigation on an intermediate scale. Mass and energy balances, as well as plate to plate compositions were calculated. After a series of methanol/ethanol distillations an HETP determination was done according to the McCabe-Thiele method. Following a large number of experimental runs under different conditions of operation, a clear-cut operating procedure was developed for use by production personnel on a routine basis. By this procedure and in accordance with uncomplicated instructions, THF can be safely recovered from the HNS synthesis effiuent at yields and purity levels that compare well with values reported in the literature.

AFRIKAANSE OPSOMMING: Heksanitrostilbeen (HNS) is 'n brisantstof wat plaaslik op loodsaanlegskaal vervaardig en op 'n eksperimentele basis as bymiddel in RDX/TNT-vullings vir die 155 mm brisantgranaat gebruik word. 'n Tegnologievestigingsprograin vir die vervaardiging van HNS is van stapel gestuur met die doel om ontwerpdata vir produksieskaaltoerusting in te samel. Tetrahidrofuraan (THF) word as oplosmirldel in die sintese van HNS gebruik. As deel van die HNS-tegnologievestigingsprogram is 'n ondersoek na die herwinning van THF, wat verreweg die duurste sintesekomponent vorm, geloods. Die ondersoek het drie fasette behels, naamlik: - 'n Kwalitatiewe ondersoek op laboratoriumskaal om die uitvoerbaarheid van distillasie as 'n herwinningsmetode te evaliJeer. - 'n Kleinskaalondersoek waartydens die herwinning van THF volgens die kontinuesowel as die enkelladingbedryfswyse ondersoek is. - 'n Ondersoek op tussenskaal waartydens 'n bepaalde bedryfsprosedure, wat op 'n roetinebasis deur produksiepersoneel vir die herwinning van THF gevolg kon word, ontwikkel is. Die ondersoek op laboratoriumskaal 'n Laboratoriumskaalherwinningsfasiliteit is vir die doel van die ondersoek uit standaardtoerusting en -instrumentasie saamgestel. In die eerste fase van die program is daar gebruik gemaak van oplosmiddelmengsels wat die HNS-sintese-afvalstroom simuleer as distillasievoer, omdat die risiko verbonde aan distillasie van die werklike afvalstroom (wat 'n klein persentasie brisantstof bevat), nie bekend was nie. Daar is bewys dat THF teen goeie opbrengste en aanvaarbare suiwerhede dmv 'n atmosferiese distillasie uit hierdie gesimuleerde afvalstroom herwin kan word. Die behandeling van die afvalstroom met HCL en ekstraheermiddels voor distillasie ten einde ongewenste komponente te verwyder, is vervolgens ondersoek. Die presipitasie van opgeloste brisantstofprodukte met Hel was suksesvol, maar die ekstraksie van THF met pentaan, tolueen en xileen het die opbrengs en suiwerheid van die herwonne produk benadeel en is derhalwe nie voortgesit nie. In 'n daaropvolgende eksperimentreeks is die werklike brisantstofafvalstroom as distillasievoer gebruik. Daar is getoon dat die afvalstroom sonder ontploffingsgevaar aan . 'n atmosftfriese distillasie onderwerp kan word. Die ondersoek op kleinskaal Soos voorheen genoem, is HNS 'n ontwikkelingsproduk wat bloot op 'n eksperimentele basis vervaardig en gebruik word. Die aangewese konsentrasie daarvan as bymiddel in RDX/TNT-vullings is nog nie kwantitatief geevalueer nie. Om hierdie rede was dit nie bekend in watter hoeveelhede HNS in die toekoms benodig en vervaardig sal word nie. Projeksies rakende die volume van die afvalstroom waaruit THF herwin moet word, was gevolglik ook nie moontlik nie. In die lig hiervan is besluit dat die herwinning yan THF uit . die HNS-sintese-afvalstroom volgens beide die kontinue- en enkelladingbedryfswyse ondersoek moet word. Vir die ondersoek na THF-herwinning op kleinskaal is modulere distilleertoerusting van glas ontwerp en vervaardig. 'n Groot aantal eksperimentele lopies is uitgevoer waartydens verskeie toerustingprobleme geidentifiseer en deur modifikasies opgelos is. Resultate het getoon dat 'n kontinue bedryfsprosedure nie uitvoerbaar is nie en die toerustingontwerp is derhalwe gewysig om vir enkelladingdistillasie voorsiening te maak. Die ondersoek op tussenskaal Toerusting van vlekvry staal is vir die ondersoek na THF-herwinning op tussenskaal ontwerp en opgerig. Massa- en energiebalanse, sowel as plaat-tot-plaat samestellings is bereken. 'n HETP-bepaling is volgens die McCabe-Thiele-metode uitgevoer na 'n reeks metanol/etanol-distillasies. 'n Bepaalde bedryfsprosedure, wat op ·'n roetinebasis deur produksiepersoneel vir die herwinning van THF gevolg kon word, is ontwikkel nadat 'n groot aantal eksperimentele lopies by verskillende bedryfskondisies uitgevoer is. Volgens hierdie prosedure kon THF veilig volgens eenvoudige instruksies uit die HNS-sinteseafvalstroom herwin word in suiwerhede en opbrengste wat goed vergelyk met waardes wat in die literatuur gerapporteer word.

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